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<br />3014
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<br />in sedimentat ion is expected. Due to the sandy nature of the so; 1, and the measures to be
<br />taken to stabilize the area of impact, no long-term effects are foreseen with regard to
<br />turbidity. No significant change of dissolved minerals in the water is anticipated. The water
<br />temperature is expected to be more uniform throughout the year than under present conditions;
<br />however, it is expected that temperatures will rise to historic levels. the further water
<br />travels downstream of the dam.
<br />
<br />8. Fish. According to the Fish and Wildlife Service, the existing sport fishing in the
<br />SoutlllfTatte River at the Narrows site is negligible. The major impact on the fishery resource
<br />would be the conversion of the lotie (riverine) environment into a lacustrine (lake) environ-
<br />ment. With the development of a fish hatchery, the reservoir is expected to provide a high
<br />quality warm-water fishery consisting of such species as walleye (Stizostedion vitreum)
<br />northern pike (Esox lucius), largemouth and smallmouth bass (Micropterus salmoides and
<br />]1. dolomieu), channel c:arnsn (Ictalurus spp.), crappie (Pomoxis spp.), and bJueglll (Lepomis
<br />macfoch1fUS). After reservoir construction, water conditlons may be favorable for the estab-
<br />lishment of a cold-water fishery immediately downstream of the damsite.
<br />
<br />9. Benthos. It is anticipated that a significant change in species composition of the benthic
<br />community would take place with impoundment. Presently, there is a limited benthic community
<br />due to the shifting sandy bottom. The benthic community is dominated by tubificids and midge
<br />larvae. These specific organisms are known to thrive in productive reservoirs and it is fully
<br />expected they would flourish with the implementation of the Narrows Unit.
<br />
<br />10. Riparian Woodlands. Dam construction on the river would cause the inundation of
<br />2,666 acres (1,079 ha) of riparian bottom lands comprised of 1,621 acres (656 ha) of open
<br />cottonwood stands, 62 acres (25 ha) of closed cottonwood stands, 749 acres (303 ha) of mixed
<br />willow-cottonwood stands, 64 acres (26 ha) of pure willow stands, and 170 acres (69 ha)
<br />of open park.
<br />
<br />11. Wetlands. A total of 2,500 acres (1,012 ha) of wetlands within the conservation pool area
<br />would be lost upon filling; however, it is expected that increased irrigation water would cause
<br />increased seep areas and ponding in low...lying areas which would support wetland invader spe-
<br />cies. The intensive wildlife management plan would impound 540 acres (219 ha) of open-water
<br />marsh. Additionally, a 13,189-acre (S,340-ha) reservoir would be .created.
<br />
<br />12. Wildlife Habitat. The loss of 13,189 acres (5,340 ha) of potential or usable wildlife
<br />habitat with,n the conservation pool would take place. This wildl ife habitat consists of
<br />irrigated cropland, sand sage, riparian woodlands (willow and willow-cottonwood) and wet meadow
<br />complexes.
<br />
<br />13. Federally Listed Endarigered and Threatened Species. As stated in the Narrows Unit
<br />Bio10 lcal 0 1n,on - Bald Ea le, Pere rlne Falcon, and Black-footed Ferret (December 2, 1r9~
<br />e propose arrows Unl s not e y to Jeopar lZe t e contmue eXlstence of the peregrine
<br />falcon (Falcoperegrinus) and black-footed ferret (Mustela nigri~es). The continued existence
<br />of winterTi'ig oald eagles (Haliaeetus leueocephalus) 1S not 11kely to be jeopardized with
<br />certain conservation stipu1atlons (preservatlon of mature roost and perch trees' and follow-up
<br />eagle studies) provided in the current wintering areas along the South Platte River (See
<br />Biological Opinion, appendix C). The conservation measures will be implemented except where
<br />structural development would require removal of mature cottonwoods.
<br />
<br />A jeopardy biological opinion on the whooping crane (Grus americana) in central Nebraska was
<br />issued on January 20, 1983, by the Fish and Wildl rre--Servlce Regional Office in Denver,
<br />Colorado. The FWS had determined that the channel width in the critical habitat reach and the
<br />available Foosting habitat would be adversely modified by reduced flows resulting from the
<br />Narrows Unit. This opinion presented an alternative to prevent the ffOject's effects and
<br />stated that 1I. . . roosting habitat can be maintained at 1,100 ft during the periods
<br />February 1 to May 10 and September 16 to November 15 . . . .11 Additionally, IIA stream power
<br />regime of 3,800 ft3 for 23 days tci maintain river channel width. . .11 was delineated. In
<br />March 1983, an interagency task group composed of staff from the Bureau and Fish and Wild] ife
<br />Service was formed to identify additional water and/or ,land management alternatives to remove
<br />the jeopardy finding rendered by the Fish and Wildlife Service. This group identified a number
<br />of alternatives which it believed could provide the suitable hab,itat characteristics conducive
<br />to continued whooping crane use in the area of concern. However, it was concluded that none of
<br />the alternatives, including the 'plan recommended in the biological opinion issued on January
<br />20, 1983, are completely satisfactory due to the lac,k of certainty that, if implemented, the
<br />desired results of providing for whooping crane habitat would be achieved.. As a result, the
<br />Regional Directors of the two Interior agencies have agreed to a plan of action to field test
<br />a number of these measures over the next 2 years with the goal of developing an acceptable
<br />and implementable plan for whooping crane habitat management that would remove the jeopardy
<br />opinion. The plan of action is contained in Appendix D.
<br />
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